Cameras are commonly used to capture an image of a scene that includes one or more objects. It is often desirable to detect the main subject of the image from the one or more objects that are present. Main subject detection is a key element in image theme understanding research. Additionally, main subject detection can be used for many different applications. For example, main subject detection can greatly benefit in-camera capture functions (e.g., better auto-focus (AF) and auto-exposure (AE), better tracking, better image/object recognition, better composition, etc.) and out-of-camera image editing functions (e.g., adaptive image compression, image retargeting, image retrieval, etc.). Unfortunately, existing methods for main subject detection have not been completely satisfactory.